Re: 1990 Chevy Truck Idle Problem
does it still do this on a cold start and before you actually have to drive anywhere?
dual exhaust with dual catalytic converters? or a single catalylic converter?
if you have one, then maybe you could try to disconnect it in front of the 'cat, then run it and see if it still does this, if it runs great (loud of course) then it could be your 'cat.
OR, bang your 'cat converter some, to knock some of the debris loose, and run it and see if that changes the pitch any